I actually say "good luck" pretty generally (you can never have too much luck). If you're referring to specific action they're about to undertake and you want to emphasize hard work, "Make it so" is another situationally useful phrase.

Slightly more generally useful might be "Make the future happen."

Is your goal to increase the emphasis on hard-work and rationality, or just have something that sounds nice that you don't disagree with? (In that case I'd just go with "good luck").